Among　all　the　preparation　methods,　electrochemical　exfoliation　of　graphite　in　neutral　aqueous　solution　to　prepare　high-quality　graphene　is　a　hot　research　topic　due　to　many　advantages,　such　as　high　efficiency,　environmental　friendly,　fewer　defects,　and　convenient　operation　with　simple　equipment.　In　this　work,　the　graphene　was　prepared　by　pre-intercalation　assisted　electrochemical　exfoliation　of　graphite　foil,　in　which　one　pre-intercalation　stage　was　performed　at　the　low　voltage　to　moderately　enlarge　the　interlayer　distance　of　graphite　foil,　and　then　graphite　electrode　was　electrochemically　exfoliated　to　produce　graphene　nanosheets　in　an　aqueous　inorganic　salt　solution　of　(NH4)2SO4.　Through　comparing　two　pretreatment　methods　of　graphite　foil　(pre-expansion　with　liquid　nitrogen　and　pre-intercalation　by　electrochemical　intercalation),　the　electrochemical　pre-intercalation　process　was　confirmed　to　avoid　the　serious　loss　of　the　graphite　electrode　during　the　liquid　nitrogen　pretreatment　and　facilitate　electrochemical　exfoliation.　Meanwhile,　the　optimum　parameters　of　pre-intercalation　were　determined.　Subsequently,　the　effect　of　applied　voltage　on　the　quality　of　obtained　graphene　(such　as　the　number　of　layers,　defects,　size,　composition)　during　the　exfoliation　stage　was　investigated　systematically,　and　especially　the　effect　of　applied　voltage　on　the　quality　and　yield　of　graphene　was　discussed　in　detail.　The　graphene　nanosheets　with　a　small　number　of　layers　(60%　is　less　than　5　layers)　were　obtained　through　two　stages　of　electrochemical　pre-intercalation　and　exfoliation.　The　structure,　morphology,　and　composition　of　the　graphene　were　analyzed　by　using　the　XRD,　SEM,　TEM,　AFM,　and　XPS.　©　2021,　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH,　DE　part　of　Springer　Nature.